1.What does it mean to have execution permission on a directory? 2.What is the c
ID: 3855706 • Letter: 1
Question
1.What does it mean to have execution permission on a directory?
2.What is the chmod command for changing the file a.out’s permissions so that the owner can read, write, and execute; the file’s group can read and execute; and everyone else can only execute.
3. Assuming the block size is 4096 bytes and physical disk block addresses are 32 bits, how many blocks can we address using the triple indirection pointer in the UFS pointer structure?
4. Consider a file system similar to the one used by UNIX with indexed allocation. How many disk I/O operations might be required to read the contents of a small local file, which fits within one block, at the directory /users/jae125/cs410/? Assume that none of the disk blocks is currently being cached.
5. What is the advantage of using a file-allocation table (FAT) to chain together the blocks of a file in linked allocation?
Explanation / Answer
1> A directory with x bit set allow the user to change directory into directory and access the files. if we don't have the execute permission the folders won't show its contents.
2> chmod 751 a.out
3> Direct blocks address: 1k * 10blocks=10240 bytes
1 indirect block: 1k/4 * 1k = 256k bytes
1 Double indirect block: 1k/4 * 1k/4 *1k =64m bytes
1 Triple indirect block: additional (1K/4) * (1K/4) * (1k/4) * 1K = 16G bytes
max file size =10240+256k+64m+16g = 17247250432 =16g bytes
4> contents of the small local file /users/jae125/cs410/ involves 5 sepa-rate disk operations Reading in the disk block containing the root directory /
reading in the disk block containing the directories users, jse125 and cs410 , and reading in the disk block containing the file in cs410 For instance, a file system could allocate 4 KB of disk space as a single 4-KB block or as eight 512-byte blocks
5> While accessing a block that stores at the middle of a file so the location can be determined by scatter the pointer store in FAT as opppsed to accessing the individual block in sequential manner to find the target block. FAT cached in memory and therefore the pointers can be determined with just having access the disk blocks.
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